Frictional material composition, frictional material, and friction member

ABSTRACT

The present invention is concerned with a frictional material composition not containing copper as an element or having the content of copper of 0.5 mass % or less, the composition containing
         (A) potassium titanate; and   (B) one or more selected from the group consisting of lithium potassium titanate and magnesium potassium titanate,   in a total content of the component (A) and the component (B) of 10 to 35 mass %, wherein   on heating a molded product of the frictional material composition to 500° C. at a temperature rise rate of 10° C./min under an air atmosphere, the mass reduction rate is 5 to 20%.

FIELD OF THE INVENTION

The present invention relates to a frictional material composition, africtional material, and a friction member.

BACKGROUND OF THE INVENTION

Frictional materials, such as a disc brake pad and a brake lining, areused for braking an automobile and the like. Such a frictional materialplays a role in the braking by rubbing an opposite material, such as adisc rotor and a brake drum. Therefore, the frictional material is notonly required to have an appropriate friction coefficient (efficacycharacteristics) according to the use condition but also required tohave such characteristics that squeal is hardly generated (squealcharacteristics) and that the life of the frictional material is long(abrasion resistance).

The frictional material is roughly classified into a semi-metallicmaterial containing, as a fiber base material, 30 to 60 mass % of asteel fiber, a low steel material containing less than 30 mass % of asteel fiber, and an NAO (Non Asbestos Organic) material not containing asteel fiber. However, a frictional material containing a minute amountof a steel fiber is also occasionally classified into the NAO material.

Since the NAO material does not substantially contain a steel fiber, ithas such a characteristic feature that it is low in aggression to a discrotor that is an opposite material, as compared with the semi-metallicmaterial and the low steel material. From such an advantage, the NAOmaterial which is excellent in a balance among the efficacy, the squeal,and the abrasion resistance is currently the mainstream in Japan, theUnited States of America, and the like. Meanwhile, in Europe, from theviewpoint of keeping the friction coefficient during high-speed braking,the low steel material was frequently used. But, in recent years, inorder to respond to the high-end market, even in Europe, the use of theNAO material that hardly generates wheel dirt of a tire and brake squealis increasing.

The NAO material is generally one containing a copper powder or fiber.But, since the frictional material containing copper contains copper inan abrasion powder produced during the braking, there is suggested apossibility that the abrasion powder leads to pollution of rivers,lakes, and so on. For that reason, the state of California and the stateof Washington of the United States of America have passed a bill toprohibit the sales of a frictional material containing 5 mass % or moreof copper and an act of assembling the foregoing frictional materialinto a new car from the year of 2021 and the sales of a frictionalmaterial containing 0.5 mass % or more of copper and an act ofassembling the foregoing frictional material into a new car from theyear of 2023.

For that reason, the development of NAO materials not containing copperor having a less content of copper is a pressing need, andinvestigations thereof are made (see, for example, JP 2002-138273 A(Patent Literature 1) and JP 2015-004037 A (Patent Literature 2)).

Then, the NAO material forms a transfer film (hereinafter also referredto as “TF”) in which the frictional material has been transferred ontothe disc rotor surface, and this TF not only contributes tostabilization of the friction coefficient but also contributes tosuppression of abrasion. For this reason, in revealing the function ofthe NAO material, it is extremely important that an appropriate amountof the TF is formed.

Examples of components which form the TF include a variety of organicmaterials in the frictional material and titanates. An organic material,such as a phenol resin, a rubber component, and a cashew dust, becomes aliquid decomposition product due to heat generated during braking,thereby forming the TF on the disc rotor surface. In addition, thetitanate, such as potassium titanate, spreads onto the frictioninterface due to braking, thereby becoming a component of the TF.

In addition, copper is also an important component in the frictionalmaterial constituting the TF. Copper is used in a powder or fiber statefor the frictional material, is high in ductility and malleability, andspreads onto the frictional material surface and the disc rotor surfacedue to braking, thereby forming the TF. In addition, copper also hassuch an effect that by smashing or burying a polishing groove duringmanufacture remaining on the brake rotor surface when it is new, theaforementioned organic decomposition product and titanate form a surfacewhich is readily fixed as the TF. However, the frictional material notcontaining copper or having a less content of copper does not have suchan action and hardly forms the TF.

Furthermore, in recent years, the diffusion of a regenerativecoordination brake is being advanced in the automobile market. Theregenerative coordination brake utilizes, as a braking force, not onlythe conventional frictional resistance by a frictional material but alsoresistance on converting a rotational force of a tire into an electricpower. In this case, in braking in a high-speed running state, in viewof the fact that the rotational force of a tire is high, and that thepower generation efficiency becomes large, the regenerative coordinationbrake is frequently used, whereas the braking by a frictional materialis restricted to a low-speed running state in which the power generationefficient of the regenerative coordination brake is low. That is, a rateof braking by the frictional material is remarkably reduced.

As a result, the amount of heat generated on the friction interfaceduring braking by the frictional material becomes small, so that the TFcomponent, such as an organic decomposition product and a titanate, ishardly transferred onto the disc rotor surface. In addition, sincecopper cannot be used from the aforementioned reasons, it becomes muchmore difficult to reveal stable frictional characteristics throughformation of the TF.

In particular, in the regenerative coordination brake, the braking iselectronically controlled, and therefore, when the frictionalcoefficient of the frictional material is not stable, a braking forcenot less than one estimated by a driver is generated to produce a suddenbraking, or reversely, a braking force desired by a driver is notobtained, so that a braking distance is extended. As a result,comfortable driving is impaired.

From this point of view, a problem of the technologies disclosed inPatent Literatures 1 and 2 is to complement frictional characteristicsduring high-load braking at the time of high-speed running by payingattention to high thermal conductivity and high-temperature lubricatingproperties of copper, but they do not take into consideration light-loadbraking from low-speed running.

Patent Literature 1 is aimed to complement the thermal conductivity andproposes a method of blending magnesium oxide and graphite in place ofcopper. However, the addition amounts of magnesium oxide that is anabrasive material and graphite that is a lubricant are extremely large,and it is difficult to improve the various frictional characteristics ina well balance.

Patent Literature 2 is aimed to complement the high-temperaturelubricating properties and proposes a method of improving the frictioncoefficient and the abrasion resistance during high-speed high-loadbraking by not only containing 1 to 15 mass % of ferrous sulfide inplace of copper but also containing 0.3 to 5 mass % of flaky graphitehaving an average particle diameter of 1 to 100 μm. However, accordingto this method, it is difficult to improve the stability of the frictioncoefficient during light-load braking.

SUMMARY OF THE INVENTION

Then, an object of the present invention is to provide a frictionalmaterial composition providing a frictional material capable ofrevealing a friction coefficient which is stable even during light-loadbraking represented by a regenerative coordination brake through acomposition with low environmental hazards and toxicity to the humanbody, which does not contain copper as an element or has the content ofcopper of 0.5 mass % or less; a frictional material; and a frictionmember using the frictional material.

The present inventors have found that a frictional material compositioncontaining a specified amount of a specified titanate and having a massreduction rate under an air atmosphere in a specified range is able tosolver the aforementioned problem, thereby leading to accomplishment ofthe present invention. Specifically, the present invention is concernedwith the following [1] to [13].

-   [1] A frictional material composition not containing copper as an    element or having the content of copper of 0.5 mass % or less, the    composition containing

(A) potassium titanate; and

(B) one or more selected from the group consisting of lithium potassiumtitanate and magnesium potassium titanate,

in a total content of the component (A) and the component (B) of 10 to35 mass %, wherein

on heating a molded product of the frictional material composition to500° C. at a temperature rise rate of 10° C./min under an airatmosphere, the mass reduction rate is from 5 to 20%.

-   [2] The frictional material composition as set forth in the above    [1], further containing (C) one or more selected from the group    consisting of zirconium silicate, zirconium oxide, and magnesium    oxide in an amount of 11 to 30 mass %.-   [3] The frictional material composition as set forth in the above    [1] or [2], further containing, as a metal powder or a metal fiber,    one or more selected from the group consisting of iron, tin, zinc,    and aluminum in an amount of 0.5 to 5 mass %.-   [4] The frictional material composition as set forth in any of the    above [1] to [3], wherein a content ratio of the component (A) and    the component (B) [(A)/(B)] is from 0.1 to 10 in terms of a mass    ratio.-   [5] The frictional material composition as set forth in any of the    above [1] to [4], further containing an organic filler in an amount    of 1 to 20 mass %.-   [6] The frictional material composition as set forth in any one of    the above [1] to [5], further containing a binder in an amount of 5    to 20 mass %.-   [7] A frictional material including a portion not containing copper    as an element or having the content of copper of 0.5 mass % or less,    the portion containing

(A) potassium titanate; and

(B) one or more selected from the group consisting of lithium potassiumtitanate and magnesium potassium titanate,

in a total content of the component (A) and the component (B) of 10 to35 mass %, wherein

on heating to 500° C. at a temperature rise rate of 10° C./min under anair atmosphere, the mass reduction rate is from 5 to 20%.

-   [8] The frictional material as set forth in the above [7], further    containing (C) one or more selected from the group consisting of    zirconium silicate, zirconium oxide, and magnesium oxide in an    amount of 11 to 30 mass %.-   [9] The frictional material as set forth in the above [7] or [8],    further containing, as a metal powder or a metal fiber, one or more    selected from the group consisting of iron, tin, zinc, and aluminum    in an amount of 0.5 to 5 mass %.-   [10] The frictional material as set forth in any of the above [7] to    [9], wherein a content ratio of the component (A) and the    component (B) [(A)/(B)] is from 0.1 to 10 in terms of a mass ratio.-   [11] The frictional material as set forth in any of the above [7] to    [10], further containing an organic filler in an amount of 1 to 20    mass %.-   [12] The frictional material as set forth in any of the above [7] to    [11], further containing a binder in an amount of 5 to 20 mass %.-   [13] A friction member including the frictional material as set    forth in any of the above [7] to [12] and a backing plate integrated    therewith.

In accordance with the present invention, it is possible to provide africtional material composition providing a frictional material capableof revealing a friction coefficient which is stable even duringlight-load braking represented by a regenerative coordination brakethrough a composition with low environmental hazards and toxicity to thehuman body, which does not contain copper as an element or has thecontent of copper of 0.5 mass % or less; a frictional material; and afriction member using the frictional material.

DETAILED DESCRIPTION OF THE INVENTION

The frictional material composition, the frictional material, and thefriction member according to the present embodiments are hereunderdescribed in detail, but it should be construed that the presentinvention is not limited to the following embodiments.

The frictional material composition and the frictional materialaccording to the present embodiments do not contain asbestos and areso-called non-asbestos frictional material composition and non-asbestosfrictional material, respectively.

[Frictional Material Composition]

The frictional material composition according to the present embodimentis a frictional material composition not containing copper as an elementor having the content of copper of 0.5 mass % or less, the compositioncontaining

(A) potassium titanate; and

(B) one or more selected from the group consisting of lithium potassiumtitanate and magnesium potassium titanate,

in a total content of the component (A) and the component (B) of 10 to35 mass %, wherein

on heating a molded product of the frictional material composition to500° C. at a temperature rise rate of 10° C./min under an airatmosphere, the mass reduction rate is 5 to 20%.

The frictional material composition according to the present embodimentdoes not contain copper as an element or has the content of copper of0.5 mass % or less. Therefore, copper is not contained in an abrasionpowder produced during braking, or the content of copper in the abrasionpowder is an infinitesimal amount, and hence, there is no concern aboutpollution of rivers, lakes, and so on. From the viewpoint of suppressingthe environmental hazards and toxicity to the human body, the content ofcopper in the frictional material composition is preferably less than0.5 mass %, more preferably 0.3 mass % or less, and still morepreferably 0.1 mass % or less, and it is especially preferred thatcopper is not contained.

The frictional material composition according to the present embodimentprovides a frictional material capable of revealing a frictioncoefficient which is stable even during light-load braking while havinga composition with low environmental hazards and toxicity to the humanbody. Although the reason why such is caused is not always elucidatedyet, the following may be conjectured.

The present inventors have studied a titanate that is essential for theformation of TF and found that though the titanate is transferred ontothe brake rotor surface due to braking, to form the TF, a sufficientamount of the TF cannot be formed through single use under a low-speedlow-load condition; and that a favorable TF is formed by regulating amass reduction rate under a specified condition to an appropriate range.This may be considered to be caused due to the matter that the massreduction rate on heating to 500° C. exhibits a thermal decompositionamount of an organic material, such as mainly an organic filler, at atemperature corresponding to frictional heat during light-load braking,and by regulating the thermal decomposition amount at a relatively lowtemperature as 500° C. to an appropriate range, a favorable TF could beformed due to a spread product of the decomposition product and thetitanate even during light-load braking.

<Mass Reduction Rate on Heating to 500° C.>

The frictional material composition according to the present embodimentis one in which on heating a molded product of the frictional materialcomposition to 500° C. at a temperature rise rate of 10° C./min under anair atmosphere, the mass reduction rate is 5 to 20%.

In this specification, in the case of referring to simply as “massreduction rate”, it means the “mass reduction rate on heating a moldedproduct of the frictional material composition to 500° C. at atemperature rise rate of 10° C./min under an air atmosphere”.

In the frictional material composition according to the presentembodiment, by regulating the mass reduction rate at 500° C.corresponding to the frictional heat during light-load braking to theaforementioned range, the thermal decomposition amount of the organicmaterial represented by the organic filler in the frictional heat duringlight-load braking is regulated to an appropriate range, whereby afavorable TF can be formed on the disc rotor surface by thedecomposition product and the titanate even during light-load braking.

On the other hand, when the mass reduction rate is less than 5%, theamount of the decomposed organic filler, etc. is poor, and a favorableTF is not formed on the disc rotor surface. In addition, when the massreduction rate is more than 20%, the amount of the decomposed organicfiller, etc. becomes excessive, and the abrasion of the frictionalmaterial is promoted.

From the aforementioned viewpoints, the mass reduction rate ispreferably 5 to 18%, more preferably 6 to 15%, and still more preferably11 to 15%.

The mass reduction rate can be measured by the method described in thesection of Examples.

The frictional material is, in general, produced by a method ofhot-press molding a pre-molded product obtained by pre-molding thefrictional material composition, or a method of directly hot-pressmolding the frictional material composition and if desired, furtherperforming a heat treatment to thermally cure the binder.

A representative condition of hot-press molding for the purpose ofobtaining a molded product which is provided for measuring the massreduction rate is the condition described in the section of Examples.That is, the method is one in which after heating at 145° C. for 5minutes, the heat treatment is performed at 200° C. for 4.5 hours.

The present invention also provides a frictional material composition inthe case of changing the aforementioned molding condition. For example,the present invention also provides a frictional material composition inwhich the molding condition is any one condition under which thetemperature is in a range of from 150 to 250° C., and the time is in arange of from 2 to 10 hours, and the mass reduction rate of a moldedproduct obtained through molding under the foregoing molding conditionsatisfies 5 to 20%.

Examples of the method of allowing the mass reduction rate to fallwithin the aforementioned range include a method of regulating the kindof an organic component which the frictional material compositioncontains and the content thereof. A cashew dust, a rubber component, andthe like which are used as the organic filler are relatively low interms of a decomposition temperature, and therefore, they are decomposedby the frictional heat generated during light-load braking, to form a TFon the disc rotor surface. In consequence, by regulating the kind ofsuch an organic component and the content thereof, the mass reductionrate on heating to a temperature of 500° C. corresponding to thefrictional heat generated during light-load braking under an airatmosphere, whereby an appropriate amount of the TF can be formed on thedisc rotor surface.

<Constituent Components of Frictional Material Composition>

Preferably, the frictional material composition according to the presentembodiment contains one or more selected from the group consisting of anorganic filler, an inorganic filler, a fiber base material, and abinder.

The respective components which the frictional material compositionaccording to the present embodiment contains are hereunder described.

<Organic Filler>

The organic filler is contained as a friction modifier to improve thesound vibration performance, the abrasion resistance, the stability ofthe friction coefficient during light-load braking, and the like of thefrictional material.

Examples of the organic filler include a cashew dust and a rubbercomponent.

The organic filler may be used alone, or may be used in combination oftwo or more thereof.

As the cashew dust, for example, any cashew dust which is obtained bygrinding a cashew nut shell oil having been polymerized and cured andwhich is typically used for a frictional material may be used.

In the case where the frictional material composition contains thecashew dust, the content thereof is preferably 1 to 10 mass %, morepreferably 2 to 8 mass %, and still more preferably 3 to 7 mass %. Whenthe content of the cashew dust falls within the aforementioned range,not only the deterioration of the sound vibration performance, such assqueal which is caused due to an increase of elastic modulus of thefrictional material, can be suppressed, but also the deterioration ofthe heat resistance and a lowering of the strength to be caused due toheat hysteresis can be suppressed. Furthermore, the stability of thefriction coefficient during light-load braking can be enhanced.

Examples of the rubber component include tire rubber, acrylic rubber,isoprene rubber, NBR (nitrile-butadiene rubber), and SBR(styrene-butadiene rubber). Of those, NBR and tire rubber are preferred,and a combined use of NBR and tire rubber is more preferred.

In the case where the frictional material composition contains therubber component, the content thereof is preferably 0.2 to 10 mass %,more preferably 0.5 to 5 mass %, and still more preferably 1 to 3 mass%.

In the frictional material composition according to the presentembodiment, a combined use of the cashew dust and the rubber componentis preferred from the viewpoint of obtaining a stable frictioncoefficient even by light-load braking.

In the case where the frictional material composition contains thecashew dust and the rubber component, a total content thereof ispreferably 2 to 20 mass %, more preferably 3 to 12 mass %, and stillmore preferably 4 to 10 mass % from the viewpoint of enhancing thestability of the friction coefficient during light-load braking.

In the case where the cashew dust and the rubber component are used incombination, the cashew dust coated with the rubber component may beused, and from the viewpoint of sound vibration performance, the cashewdust and the rubber component may be separately blended.

The median diameter (D50) of cashew dust is preferably 1 to 800 μm, andmore preferably 10 to 500 μm, still more preferably 50 to 400 μm.

A total content of the organic filler in the frictional materialcomposition is preferably 2 to 20 mass %, more preferably 3 to 12 mass%, and still more preferably 4 to 10 mass %. When the total content ofthe organic filler falls within the aforementioned range, thedeterioration of the sound vibration performance, such as squeal whichis caused due to an increase of elastic modulus of the frictionalmaterial, can be suppressed, and the deterioration of the heatresistance and a lowering of the strength to be caused due to heathysteresis can be suppressed.

<Inorganic Filler>

The inorganic filler is contained as the friction modifier to be usedfor the purpose of revealing a stable friction coefficient even bylight-load braking and the purpose of avoiding the deterioration of theheat resistance of the friction material.

The inorganic filler may be used alone, or may be used in combination oftwo or more thereof.

The friction material composition according to the present embodimentcontains (A) potassium titanate (hereinafter also referred to as“component (A)”) and (B) one or more selected from the group consistingof lithium potassium titanate and magnesium potassium titanate(hereinafter also referred to as “component (B)”). Preferably, thefriction material composition according to the present embodimentfurther contains (C) one or more selected from the group consisting ofzirconium silicate, zirconium oxide, and magnesium oxide (hereinafteralso referred to as “component (C)”).

(Component (A) and component (B))

The component (A) and the component (B) spread onto the frictioninterface due to braking, thereby contributing to formation of afavorable TF. On the other hand, in the case where the frictionalmaterial composition contains the component (A) only without containingthe component (B), the deterioration of the abrasion resistanceoccasionally becomes problematic, whereas in the case where thefrictional material composition contains the component (B) only withoutcontaining the component (A), an extreme lowering of the frictioncoefficient occasionally becomes problematic.

A total content of the component (A) and the component (B) in thefrictional material composition is 10 to 35 mass %, preferably 13 to 30mass %, and more preferably 15 to 25 mass %. When the aforementionedtotal content is 10 mass % or more, the stability of the frictioncoefficient is improved, whereas when it is 35 mass % or less, anextreme increase of porosity is suppressed, and a lowering of themechanical strength of the frictional strength, a lowering of thestability of the friction coefficient to be caused due to moistureabsorption, and adherence between the frictional material and theopposite material to be caused due to a rust can be suppressed.

A content ratio of the component (A) and the component (B) in thefrictional material composition [(A)/(B)] is preferably 0.1 to 10, morepreferably 0.5 to 2, and still more preferably 0.8 to 1.2 in terms of amass ratio from the viewpoint of the stability of the frictioncoefficient during light-load braking.

Examples of the component (A) include potassium octatitanate andpotassium hexatitanate.

A median diameter (D50) of the component (A) is preferably 1 to 30 μm,more preferably 2 to 20 μm, and still more preferably 3 to 15 μm.

The component (B) is one or more selected from the group consisting oflithium potassium titanate and magnesium potassium titanate. Thecomponent (B) may be an embodiment containing lithium potassium titanateonly and not containing magnesium potassium titanate, or may be anembodiment containing magnesium potassium titanate only and notcontaining lithium potassium titanate according to a desiredperformance.

A median diameter (D50) of the component (B) is preferably 1 to 50 μm,more preferably 5 to 45 μm, and still more preferably 8 to 40 μm.

The component (A) and the component (B) are not restricted with respectto the particle size, the shape, and the like so long as thecharacteristic are not extremely deteriorated, and for example, theshape may be acicular, platy, granular, amoebic, or the like.

<Component (C)>

The component (C) is one or more selected from the group consisting ofzirconium silicate, zirconium oxide, and magnesium oxide and acts as anabrasive material.

The content of the component (C) in the frictional material compositionis preferably 11 to 30 mass %, more preferably 11 to 25 mass %, andstill more preferably 11 to 22 mass %. When the aforementioned contentis 11 mass % or more, the aggression to the disc rotor that is anopposite material is appropriately imparted, a polishing groove duringmanufacture remaining on the brake rotor surface when it is new ispolished, whereby a surface on which the TF is more readily fixed can beformed. Meanwhile, when the content of the component (C) is 30 mass % orless, the abrasion of the disc rotor can be suppressed without makingthe aggression to the disc rotor excessive.

The median diameter (D50) of magnesium oxide is preferably 1 to 50 μm,and more preferably 3 to 20 μm.

In the case where one selected from the group consisting of zirconiumsilicate, zirconium oxide, and magnesium oxide is contained as thecomponent (C), an embodiment in which the remaining two are notcontained may be adopted, and in the case where two selected from thegroup consisting of zirconium silicate, zirconium oxide, and magnesiumoxide are contained as the component (C), an embodiment in which theremaining one is not contained may also be adopted.

A median diameter (D50) of the component (C) is preferably 0.5 to 30 μm,more preferably 0.5 to 20 μm, and still more preferably 0.5 to 15 μm.When the median diameter (D50) of the component (C) is 0.5 μm or more,favorable friction coefficient and aggression to the disc rotor arerevealed, whereas when it is 30 μm or less, not only the dispersibilityon the friction interface can be enhanced, and the friction coefficientcan be made stable, but also the matter that the aggression to theopposite material becomes extremely high can be avoided.

The median diameter (D50) of zirconium silicate is preferably 0.5 to 5μm, and more preferably 0.6 to 2 μm.

The median diameter (D50) of zirconium oxide is preferably 2 to 15 μm,and more preferably 5 to 10 μm.

The median diameter (D50) of the component (C) can be measured byadopting a method, such as laser diffraction particle size distributionmeasurement. For example, the measurement can be performed with a laserdiffraction/scattering type particle size distribution analyzer (tradename: LA-920 (manufactured by Horiba, Ltd.)).

(Other Inorganic Filler)

The frictional material composition according to the present embodimentmay contain an inorganic filler other than the aforementioned respectivecomponents within a range where the effects of the present embodimentare not impaired.

Examples of the other inorganic filler include tin sulfide, molybdenumdisulfide, iron sulfide, bismuth sulfide, zinc sulfide, calciumhydroxide, calcium oxide, sodium carbonate, calcium carbonate, magnesiumcarbonate, barium sulfate, dolomite, coke, graphite, mica, iron oxide,vermiculite, calcium sulfate, talc, clay, zeolite, mullite, chromite,titanium oxide, activated alumina, such as γ-alumina, and silica. Ofthose, one or more selected from the group consisting of graphite, tinsulfide, mica, calcium hydroxide, and barium sulfate are preferred.

In the case where the frictional material composition contains graphite,the content thereof is, for example, 0.5 to 10 parts by mass, andpreferably 1 to 3 parts by mass.

In the case where the frictional material composition contains tinsulfide, the content thereof is, for example, 0.5 to 10 parts by mass,and preferably 1 to 3 parts by mass.

In the case where the frictional material composition contains calciumhydroxide, the content thereof is, for example, 0.5 to 10 parts by mass,and preferably 1 to 3 parts by mass.

In the case where the frictional material composition contains bariumsulfate, the content thereof is, for example, 1 to 60 parts by mass, andpreferably 5 to 50 parts by mass.

In the case where the frictional material composition contains otherinorganic filler, the total content is preferably 5 to 70 mass %, morepreferably 10 to 65 mass %, and still more preferably 15 to 60 mass %.

A total content of the inorganic filler in the frictional materialcomposition is preferably 20 to 80 mass %, more preferably 30 to 80 mass%, and still more preferably 40 to 80 mass % from the viewpoint ofproviding a frictional material which is excellent in heat resistanceand reveals a stable friction coefficient even by light-load braking.

<Fiber Base Material>

Preferably, the frictional material composition according to the presentembodiment further contains a fiber base material. The fiber basematerial exhibits a reinforcing action or the like in the frictionalmaterial.

Examples of the fiber base material include an organic fiber, aninorganic fiber, and a metal fiber.

The fiber base material may be used alone, or may be used in combinationof two or more thereof.

Examples of the organic fiber include an aramid fiber, an acrylic fiber,a cellulose fiber, and a phenol resin fiber. Of those, an aramid fiberis preferred from the viewpoints of heat resistance and reinforcingeffect.

In the case where the frictional material composition according to thepresent embodiment contains an organic fiber, the content thereof is 0.5to 10 mass %, more preferably 1 to 5 mass %, and still more preferably 2to 4 mass %.

Examples of the inorganic fiber include wollastonite, a ceramic fiber, abiodegradable ceramic fiber, a mineral fiber, a carbon fiber, a glassfiber, a potassium titanate fiber, and an aluminosilicate fiber.However, it is preferred that an inhalant potassium titanate fiber orthe like is not contained from the viewpoint of toxicity to the humanbody.

In this specification, it should be construed that the metal fiber isnot included in the definition of the inorganic fiber.

The aforementioned mineral fiber is an artificial inorganic fiber inwhich blast furnace slag for slag wool, basalt for basalt fiber, andother natural stone are melt-spun as the main component. The mineralfiber is preferably a natural mineral containing an Al element.Specifically, there is exemplified one containing one or more of SiO₂,Al₂O₃, CaO, MgO, FeO, Na₂O, and the like. Of those, a mineral fibercontaining an Al element is preferred.

An average fiber length of the mineral fiber is preferably 500 μm orless, and more preferably 100 to 400 μm. When the average fiber lengthis the aforementioned upper limit value or less, the bond strength witheach of the components in the frictional material composition tends tobecome favorable. The average fiber length as referred to herein refersto a number average fiber length indicating an average value of thelengths of the corresponding fibers. For example, the average fiberlength of 200 μm indicates that when 50 mineral fibers to be used as theraw material of the frictional material composition are randomlyselected and then measured for the fiber length with an opticalmicroscope, an average value thereof is 200 μm.

In the case where the frictional material composition according to thepresent embodiment contains an inorganic fiber, the content thereof ispreferably 0.5 to 10 mass %, more preferably 1 to 5 mass %, and stillmore preferably 2 to 4 mass %.

Examples of the metal fiber include an iron-based fiber, a titaniumfiber, a zinc fiber, and an aluminum fiber.

In the case where the frictional material composition according to thepresent embodiment contains a metal fiber, the content thereof ispreferably 0.5 to 5 mass %, more preferably 0.6 to 2 mass %, and stillmore preferably 0.7 to 1 mass %.

The frictional material composition according to the present embodimentmay also be one not containing a metal fiber according to a desiredperformance.

In the case where the frictional material composition according to thepresent embodiment contains a fiber base material, the total content ispreferably 4 to 40 mass %, more preferably 5 to 20 mass %, and stillmore preferably 6 to 10 mass %. When the total content of the fiber basematerial falls within the aforementioned range, it is possible to impartan appropriate reinforcing effect to the frictional material withoutgiving a harmful influence, such as a remarkable lowering of efficacycharacteristics.

<Binder>

Preferably, the frictional material composition according to the presentembodiment contains a binder. The binder has an action of integratingthe organic filler, the fiber base material, and the like contained inthe frictional material composition with each other, thereby imparting astrength.

The binder may be used alone, or may be used in combination of two ormore thereof.

As the binder, a thermosetting resin which is typically used for africtional material composition can be used.

Examples of the thermosetting resin include a phenol resin; and avariety of modified phenol resins, such as an acrylic rubber-modifiedphenol resin, a silicone rubber-modified phenol resin, a cashew-modifiedphenol resin, an epoxy-modified phenol resin, and analkylbenzene-modified phenol resin. Of those, a phenol resin, an acrylicrubber-modified phenol resin, a silicone rubber-modified phenol resin,and an alkylbenzene-modified phenol resin are preferred from theviewpoint of providing favorable heat resistance, moldability, andfriction coefficient.

The content of the binder in the frictional material composition ispreferably 5 to 20 mass %, more preferably 7 to 15 mass %, and stillmore preferably 8 to 12 mass %. When the content of the binder fallswithin the aforementioned range, not only an excellent strength can beimparted to the frictional material, but also the porosity of thefrictional material is reduced, whereby the deterioration of the soundvibration performance, such as squeal which is caused due to an increaseof elastic modulus, can be suppressed.

<Metal Powder>

The frictional material composition according to the present embodimentmay contain a metal powder.

Examples of the metal powder include an iron powder, a tin powder, azinc powder, an aluminum powder, and an alloy powder thereof. The metalpowder may be used alone, or may be used in combination of two or morethereof.

In the case where the frictional material composition according to thepresent embodiment contains a metal powder, the content thereof ispreferably 0.5 to 5 mass %, more preferably 0.5 to 3 mass %, and stillmore preferably 1 to 2 mass %. When the content of the metal powder is0.5 mass % or more, the metal powder not only forms a TF on the discrotor surface but also polishes or buries a polishing groove of the discrotor when it is new, whereby the disc rotor surface on which a TF madeof the organic filler, the titanate, the metal powder, and the like isreadily fixed is produced, and the friction coefficient duringlight-load braking becomes stable. In addition, when the content of themetal powder is 5 mass % or less, excessive intermetallic adhesion orthe like is suppressed, whereby extreme abrasion and deterioration ofthe frictional material and the disc rotor can be avoided.

The metal powder is not restricted with respect to the particle size,the shape, and the like so long as the characteristic are not extremelydeteriorated. The shape may be a spherical shape produced by a generalatomizing method or the like, or a columnar shape produced by a generalcutting method or the like. In addition, though the purity as the metalis preferably 90% or more, the metal powder surface may be changed to ametal oxide or the like due to long-term storage of the metal powder andthe frictional material, or the like.

The frictional material composition according to the present embodimentmay also be one not containing a metal powder according to a desiredperformance.

Preferably, the frictional material composition according to the presentembodiment contains, as the metal powder or the metal fiber, one or moreselected from the group consisting of iron, tin, zinc, and aluminum.

In the case where the frictional material composition according to thepresent embodiment contains one or more selected from the groupconsisting of iron, tin, zinc, and aluminum, the content thereof ispreferably 0.5 to 5 mass %, more preferably 0.6 to 4 mass %, and stillmore preferably 0.7 to 3.5 mass %.

<Other Component>

The frictional material composition according to the present embodimentmay contain other component than the aforementioned respectivecomponents, as the need arises.

<Frictional Material Produced by Molding the Frictional MaterialComposition According to the Present Embodiment>

The present invention also provides a frictional material produced bymolding the frictional material composition according to the presentembodiment.

The frictional material produced by molding the frictional materialcomposition according to the present embodiment can be, for example,produced by a method of hot-press molding a pre-molded product obtainedby pre-molding the frictional material composition according to thepresent embodiment, or a method of directly hot-press molding thefrictional material composition according to the present embodiment andif desired, further performing a heat treatment to thermally cure thebinder. A specific production method is described in the productionmethod of the frictional material according to the present embodiment asmentioned later and in the section of Examples.

[Frictional Material and Friction Member]

The frictional material according to the present embodiment is africtional material including a portion not containing copper as anelement or having the content of copper of 0.5 mass % or less, theportion containing

(A) potassium titanate; and

(B) one or more selected from the group consisting of lithium potassiumtitanate and magnesium potassium titanate,

in a total content of the component (A) and the component (B) of 10 to35 mass %, wherein

on heating to 500° C. at a temperature rise rate of 10° C./min under anair atmosphere, the mass reduction rate is 5 to 20%.

The kind and content of each of the components to be contained in thefrictional material according to the present invention as well as themass reduction rate are those the same as described for theaforementioned frictional material composition according to the presentembodiment, and preferred embodiments thereof are all the same, too.

<Production Method of Frictional Material>

The frictional material according to the present embodiment can beproduced by a generally adopted method by using the frictional materialcomposition according to the present embodiment. Specifically, thefrictional material according to the present embodiment can be, forexample, produced by uniformly mixing the frictional materialcomposition according to the present embodiment by using a mixer, suchas a Loedige (registered trademark) mixer, a pressure kneader, and anEirich (registered trademark) mixer; pre-molding this mixture using amolding mold; molding the obtained pre-molded product under a conditionat a molding temperature of 130 to 160° C. and a molding pressure of 20to 50 MPa for a molding time of 2 to 10 minutes; and subjecting theobtained molded product to a heat treatment at 150 to 250° C. for 2 to10 hours. The resultant may be further subjected to coating, a scorchingtreatment, a polishing treatment, etc., as the need arises.

In the thus produced new frictional material, the mass reduction rate ofthe entirety of the frictional material has only to be in a range offrom 5 to 20%. In addition, in the used frictional material, since it issubjected to heat hysteresis by the frictional heat generated duringbraking, the mass reduction rate of a portion of the frictional materialafter eliminating a portion having been subjected to heat hysteresis hasonly to be in a range of from 5 to 20%.

In the production process of the frictional material, there isoccasionally performed a scorching treatment in such a manner that theheat hysteresis by the frictional heat generated during the braking ispreviously given onto the surface of a new frictional material, so as tonot change the efficacy of braking from the initial stage of use to therepeated use. The frictional material which has been subjected to ascorching treatment in this way is automatically already subjected toheat hysteresis even in a new frictional material. Even in this case,the mass reduction rate of a portion of the frictional material aftereliminating a portion having been subjected to heat hysteresis has onlyto be in a range of from 5 to 20%.

In the case of a new frictional material which has not been subjected toa scorching treatment, the aforementioned mass reduction rate can beexamined from a decrease of mass on the occasion of performingthermogravimetric analysis (TG) using a sample obtained by shaving-outfrom the surface of the frictional material surface. In addition, in thecase of a frictional material having been subjected to a scorchingtreatment, or in the case of a repeatedly used frictional material, themass reduction rate of the frictional material can be examined by usinga sample obtained by shaving-out from the surface after eliminating aportion having been subjected to a heat hysteresis.

<Application of Frictional Material>

The frictional material according to the present embodiment is used forthe following embodiments (1) to (3).

(1) A configuration of a frictional material only.

(2) A configuration including a backing plate and a frictional materialformed on the backing plate, the frictional material being thefrictional material according to the present embodiment serving as africtional surface.

(3) A configuration further including, in the configuration of the above(2), a primer layer for the purpose of surface modification forenhancing a bonding effect of the backing plate between the backingplate and the friction member; and a bonding layer for the purpose ofbonding between the backing plate and the friction member.

Of those, it is preferred to use the frictional material as a frictionmember including the frictional material according to the presentembodiment having the backing plate integrated therewith, as in theabove (2) or (3).

The aforementioned backing plate is used for the purpose of improvingthe mechanical strength of the friction member, and examples of amaterial thereof include metals, such as iron and stainless steel; andfiber-reinforced plastics, such as an inorganic fiber-reinforced plasticand a carbon fiber-reinforced plastic.

As the aforementioned primer layer and bonding layer, any materials maybe used as long as typically used for a friction member, such as a brakeshoe.

The frictional material according to the present embodiment is suitableas a frictional material for a disc brake pad and a brake lining of anautomobile, etc. In addition, the frictional material according to thepresent embodiment can be used as a frictional material for a clutchfacing, an electromagnetic brake, a retaining brake, etc., by subjectingthe friction material to processes, such as molding, processing, andbonding to obtain desired shapes.

Furthermore, the frictional material according to the present embodimentis useful as an “over layer” of the friction member, such as a discbrake pad and a brake lining, because it is excellent in stability ofthe friction coefficient, abrasion resistance at high temperatures, etc.The frictional material can also be used upon being formed as an “underlayer” of the friction member. The “over layer” is the frictionalmaterial serving as a frictional surface of the friction member. The“under layer” is a layer placed between the frictional material servingas a frictional surface of the friction member and the backing plate forthe purpose of improving the shear strength and the anti-crackproperties in the vicinity of the bonding part between the frictionalmaterial and the backing plate.

EXAMPLES

The frictional material composition and the frictional materialaccording to the present embodiments are hereunder described in moredetail by reference to Examples, but it should be construed that thepresent invention is by no means limited thereto.

Examples 1 to 7 and Comparative Examples 1 to 6

[Production of Disc Brake Pad]

Respective materials were blended according to blending amounts shown inTable 1, to obtain frictional material compositions of Examples 1 to 7and Comparative Examples 1 to 6.

Next, each of the frictional material compositions was mixed using aLoedige mixer (manufactured by MATSUBO Corporation, a product name:Loedige mixer M20). This mixture was pre-molded with a molding press(manufactured by OJIKIKAI CO., LTD). Subsequently, the obtainedpre-molded product was hot press-molded together with a backing plate(made of iron) (manufactured by Hitachi Automotive Systems, Ltd.) usinga molding press (SANKI SEIKO CO., LTD.) under a condition at a moldingtemperature of 145° C. and a molding pressure of 35 MPa for a moldingtime of 5 minutes. Subsequently, the obtained molded article was heatedat 200° C. for 4.5 hours, polished with a rotary polisher, and thensubjected to a scorching treatment at 500° C., to obtain a disc brakepad (frictional material thickness: 9.5 mm, frictional materialprojected area: 52 cm²).

Various materials used in the Examples and Comparative Examples are asfollows.

[Binder]

-   -   Resin A (phenol resin): “HP491UP”, manufactured by Hitachi        Chemical Co., Ltd.    -   Resin B (phenol resin): “PR1950W”, manufactured by Hitachi        Chemical Co., Ltd.        [Organic Filler]    -   Cashew dust: “FF-1051”, manufactured by Tohoku Chemical        Industries, Ltd.    -   Rubber component A (tire rubber powder): “Powder TPA”,        manufactured by CAR QUEST Co., Ltd.    -   Rubber component B (nitrile butadiene rubber): “Nipol 1411”,        manufactured by Zeon Corporation        [Inorganic Filler]    -   Titanate A (potassium octatitanate): “Terracess TF-S”,        manufactured by Otsuka Chemical Co., Ltd. (shape: flaky, median        diameter (D50): 7 μm)    -   Titanate B (lithium potassium titanate): “Terracess L”,        manufactured by Otsuka Chemical Co., Ltd. (shape: flaky, median        diameter (D50): 25 μm)    -   Titanate C (magnesium potassium titanate): “Terracess PCS”,        manufactured by Otsuka Chemical Co., Ltd.    -   Barium sulfate    -   Graphite    -   Tin sulfide    -   Mica    -   Calcium hydroxide    -   Abrasive material A (zirconium silicate): “MZ1000B”,        manufactured by DAIICHI KIGENSO KAGAKU KOGYO CO., LTD. (median        diameter (D50): 1.6 μm)    -   Abrasive material B (zirconium oxide): “BR-QZ”, manufactured by        DAIICHI KIGENSO KAGAKU KOGYO CO., LTD. (median diameter (D50):        6.5 μm)    -   Abrasive material C (magnesium oxide): Magnesium Oxide 2000 for        industrial use, manufactured by Kyowa Chemical Industry Co.,        Ltd.        [Fiber Base Material]    -   Aramid fiber (organic fiber)    -   Mineral fiber (inorganic fiber)    -   Copper fiber    -   Iron fiber: #0, manufactured by GMT        [Metal Powder]    -   Zinc powder: “Zn-At-200”, manufactured by Fukuda Metal Foil &        Powder Co., Ltd. (average particle diameter: 25 to 38 μm)    -   Tin powder: “AT-Sn No. 200”, manufactured by Yamaishi Metal Co.,        Ltd. (median diameter (D50): 23 μm)    -   Aluminum powder: “VA-40”, manufactured by Yamaishi Metal Co.,        Ltd.        [Mass Reduction Rate at 500° C.]

With respect to the disc brake pad obtained in each of the Examples, themass reduction rate when heated at 500° C. under an air atmosphere wasevaluated by performing thermogravimetric analysis (TG), while definingthe content of the organic filler which may serve as a TF-formingcomponent as an index. The mass reduction rate was calculated on thebasis of the following formula.Mass reduction rate (%)=(Weight reduction amount)×100/(Weight beforethermogravimetric analysis)

For the evaluation, a sample collected from a layer in a depth of 2 to 3mm from the surface of a new frictional material was used. Forshaving-out of the sample, a milling cutter, an endmill, or the like wasused. In the case where the particle size of the shaven-out sample waslarge, the sample was regulated with a mortar to a particle size suitedfor the thermogravimetric analysis. A measurement condition of thethermogravimetric analysis was set as follows.

(Measurement Condition)

-   -   Measurement device: Thermo plus EVO TG8120, manufactured by        Rigaku Corporation    -   Measurement atmosphere: Air atmosphere    -   Measurement temperature range: 25 to 800° C.    -   Temperature rise rate: 10° C./min    -   Sample amount: 10 mg    -   Sample vessel: Alumina-made

In the thermogravimetric analysis results obtained under theaforementioned measurement condition, the mass reduction rate at 500° C.was calculated, and the evaluation was performed according to thefollowing evaluation criteria. The results are shown in Table 1.

(Evaluation Criteria)

A: 11% or more and 15% or less

B: 5% or more and less than 11%, or more than 15% and 20% or less

C: 0% or more and less than 5%, or more than 20%

With respect to the disc brake pad obtained in each of the Examples, theevaluation of various performances was performed using a brake dynamotester (manufactured by Shin Nippon Tokki Co., Ltd.). In the experiment,the evaluation was performed in terms of an inertia moment of a half ofSkyline V35, manufactured by Nissan Motor Co., Ltd. by using a Colettetype caliper of general pin-slide type and a ventilated disc rotor(FC250) (gray cast iron), manufactured by Kiriu Corp.

[Evaluation of Friction Coefficient (Efficacy Characteristics) at the100th Time of Light-Load Braking]

The braking at a vehicle speed of 40 km/h and 0.1 G was repeated 100times at a disc rotor temperature of 50° C. at the starting time ofbraking, thereby measuring a friction coefficient at the 100th time ofbraking. In general, since the surface of a new frictional material hasnot been subjected to a running-in operation yet, the contact area withthe disc rotator is small, and furthermore, the TF is not formed, sothat the friction coefficient is low. When the braking is repeated, thefriction coefficient increases and becomes stable. However, in thelight-load braking at the aforementioned vehicle speed and decelerationand low disc rotor temperature, the friction coefficient becomes hardlystable. The friction coefficient was evaluated according to thefollowing evaluation criteria. The results are shown in Table 1.

(Evaluation Criteria)

A: 0.37 or more and less than 0.43

B: 0.34 or more and less than 0.37, or 0.43 or more and less than 0.47

C: Less than 0.34, or 0.47 or more

[Evaluation of Abrasion Resistance at 400° C.]

An abrasion loss of each of the disc pads at a brake temperature priorto braking of 400° C. and 1000th time of braking was measured inconformity with JASO C427 and evaluated according to the followingevaluation criteria. The results are shown in Table 1.

(Evaluation criteria)

A: Less than 0.60 mm

B: 0.60 mm or more and less than 1.00 mm

C: 1.00 mm or more

TABLE 1 Example Item 1 2 3 4 5 6 7 Blending Binder Resin A 10 10 10 10 00 0 amount Resin B 0 0 0 0 10 10 10 (mass %) Organic Cashew dust 4 5 5 65 5 7 filler Rubber component A 1 2 2 2 2 0 0 Rubber component B 0 0 0 00 2 3 Inorganic Component (A) Titanate A 5 10 10 15 5 10 15 fillerComponent (B) Titanate B 5 10 0 15 5 10 15 Titanate C 0 0 10 0 0 0 0Component (C) Abrasive material A 0 0 0 0 3 3 0 Abrasive material B 1212 0 30 15 25 15 Abrasive material C 0 0 12 0 0 0 0 Graphite 2 2 2 2 2 22 Tin sulfide 2 2 2 2 2 2 2 Mica 2 2 2 2 2 2 2 Calcium hydroxide 2 2 2 22 2 2 Barium sulfate 49 36 36 7 40 19 18 Fiber base Aramid fiber 3 3 3 33 3 3 material Mineral fiber 3 3 3 3 3 3 3 Copper fiber 0 0 0 0 0 0 0Iron fiber 0 1 0 0 0 1 2 Metal Zinc powder 0 0 1 0 0 1 1 powder Tinpowder 0 0 0 1 0 0 0 Aluminum powder 0 0 0 0 1 0 0 Evaluation Massreduction rate at 500° C. B A A A A A B results (10%) (12%) (13%) (14%)(13%) (13%) (17%) Friction coefficient at the 100th time of A A A A A AA light-load braking (0.37) (0.38) (0.37) (0.39) (0.40) (0.41) (0.38)Abrasion resistance at 400° C. B A A B B A B (0.65) (0.51) (0.49) (0.85)(0.91) (0.57) (0.71) Comparative Example Item 1 2 3 4 5 6 BlendingBinder Resin A 6 10 10 10 0 8 amount Resin B 0 0 0 0 12 0 (mass %)Organic Cashew dust 3 5 5 5 10 3 filler Rubber component A 0 2 2 2 5 1Rubber component B 0 0 0 0 2 0 Inorganic Component (A) Titanate A 10 200 3 10 15 filler Component (B) Titanate B 10 0 20 3 10 0 Titanate C 0 00 0 0 0 Component (C) Abrasive material A 0 9 0 0 3 0 Abrasive materialB 12 10 10 10 20 15 Abrasive material C 0 0 0 0 0 0 Graphite 2 2 2 2 2 2Tin sulfide 2 2 2 2 2 2 Mica 2 2 2 2 2 2 Calcium hydroxide 2 2 2 2 2 2Barium sulfate 45 39 39 53 12 34 Fiber base Aramid fiber 3 3 3 3 3 3material Mineral fiber 3 3 3 3 3 3 Copper fiber 0 0 0 0 0 10 Iron fiber0 0 0 0 1 0 Metal Zinc powder 0 0 0 0 1 0 powder Tin powder 0 0 0 0 0 0Aluminum powder 0 0 0 0 0 0 Evaluation Mass reduction rate at 500° C. CA A A C B results (4%) (13%) (12%) (13%) (21%) (10%) Frictioncoefficient at the 100th time of C A C C B A light-load braking (0.32)(0.40) (0.30) (0.31) (0.36) (0.40) Abrasion resistance at 400° C. B C AA C A (0.68) (1.07) (0.47) (0.55) (1.10) (0.55)

Examples 1 to 7 exhibited the friction coefficient and abrasionresistance on the same levels with Comparative Example 6 containingcopper. That is, it is noted that the frictional material compositionaccording to the present embodiment is a composition with lowenvironmental hazards and toxicity to the human body, which does notcontain copper as an element or has the content of copper of 0.5 mass %or less, and it is able to reveal a stable friction coefficient evenduring light-load braking.

On the other hand, Comparative Example 1 with a small mass reductionrate at 500° C., Comparative Example 2 containing potassium titanateonly as the titanate, Comparative Example 3 containing lithium potassiumtitanate only as the titanate, Comparative Example 4 which contains bothpotassium titanate and lithium potassium titanate, but a total contentthereof is small, and Comparative Example 5 in which the mass reductionrate at 500° C. is extremely large were inferior with respect to any ofat least the friction coefficient or the abrasion resistance.

INDUSTRIAL APPLICABILITY

As compared with conventional products, in accordance with thefrictional material composition of the present invention, even if notusing copper with a high environmental load, an appropriate amount of TFis formed even during light-load braking, thereby revealing a stablefriction coefficient. Thus, the frictional material composition of thepresent invention is suitable for a frictional material and a frictionmember, such as a braking pad, etc. for not only general passenger carsbut also passenger cars mounted with a regenerative coordination brake.

The invention claimed is:
 1. A frictional material composition notcontaining copper as an element or having the content of copper of 0.5mass % or less, the composition comprising: (A) potassium titanate in anamount of 5 mass % or more; (B) one or more selected from the groupconsisting of lithium potassium titanate and magnesium potassiumtitanate in an amount of 5 mass % or more; (C) one or more selected fromthe group consisting of zirconium silicate, zirconium oxide, andmagnesium oxide in an amount of 12 to 30 mass %; one or more selectedfrom the group consisting of iron, tin, zinc, and aluminum in an amountof 0 to 3 mass % as a metal powder or a metal fiber; barium sulfate inan amount of 7 to 49 mass %; wherein: a total content of the component(A) and the component (B) is 10 to 30 mass %, and on heating a moldedproduct of the frictional material composition to 500° C. at atemperature rise rate of 10° C./min under an air atmosphere, the massreduction rate is from 10-17%.
 2. The frictional material compositionaccording to claim 1, wherein the one or more selected from the groupconsisting of iron, tin, zinc, and aluminum is present in an amount of0.5 to 3 mass %.
 3. The frictional material composition according toclaim 1, wherein a content ratio of the component (A) and the component(B) [(A)/(B)] is from 0.1 to 10 in terms of a mass ratio.
 4. Thefrictional material composition according to claim 1, further comprisingan organic filler in an amount of 2 to 20 mass %.
 5. The frictionalmaterial composition according to claim 1, further comprising a binderin an amount of 5 to 20 mass %.
 6. A frictional material including aportion not containing copper as an element or having the content ofcopper of 0.5 mass % or less, the portion comprising: (A) potassiumtitanate in an amount of 5 mass % or more; (B) one or more selected fromthe group consisting of lithium potassium titanate and magnesiumpotassium titanate in an amount of 5 mass % or more; (C) one or moreselected from the group consisting of zirconium silicate, zirconiumoxide, and magnesium oxide in an amount of 12 to 30 mass %; one or moreselected from the group consisting of iron, tin, zinc, and aluminum inan amount of 0 to 3 mass % as a metal powder or a metal fiber; bariumsulfate in an amount of 7 to 49 mass %; wherein: a total content of thecomponent (A) and the component (B) is 10 to 30 mass %, and on heatingto 500° C. at a temperature rise rate of 10° C./min under an airatmosphere, the mass reduction rate is from 5 to 20%.
 7. The frictionalmaterial according to claim 6, wherein the one or more selected from thegroup consisting of iron, tin, zinc, and aluminum in present in anamount of 0.5 to 3 mass %.
 8. The frictional material according to claim6, wherein a content ratio of the component (A) and the component (B)[(A)/(B)] is from 0.1 to 10 in terms of a mass ratio.
 9. The frictionalmaterial according to claim 6, further comprising an organic filler inan amount of 2 to 20 mass %.
 10. The frictional material according toclaim 6, further comprising a binder in an amount of 5 to 20 mass %. 11.A friction member comprising the frictional material according to claim6 and a backing plate integrated therewith.